1. Field of the Invention
The present invention relates to an antenna duplexer and a communication apparatus used in radio devices such as mobile communication devices.
2. Description of the Related Art
Antenna duplexers are high-frequency devices used in radio devices such as mobile phones for separating transmit waves from receive waves. As mobile phones have become smaller and more powerful, there has emerged a need for further reduction in size and improvement in performance of the antenna duplexers.
A typical antenna duplexer includes a receiving filter, a transmitting filter, and a matching circuit. A transmit wave is provided from a transmitter circuit to the matching circuit through the transmitting filter, subjected to matching in the matching circuit, and then guided to the antenna. A receive wave is provided from the antenna to the matching circuit, subjected to matching there, and then guided to a receiver circuit through the receiving filter.
FIG. 15 shows a perspective view of a first antenna duplexer according to the prior art. The first antenna duplexer uses a SAW (Surface Acoustic Wave) filter as a transmitting filter 50. The duplexer uses as a receiving filter 52 a dielectric coaxial filter having a coaxial resonator. The transmitting filter 50 and the receiving filter 52 are implemented on a circuit board 53.
Because the transmitting filter 50 used is the small SAW filter and the receiving filter 52 is the dielectric coaxial filter having the coaxial resonator, which provides a high Q-value and small insertion loss, the first antenna duplexer exhibits a sufficiently small insertion loss in receive waves and improved spectral separation and has a reduced size in its entirety.
FIG. 16 shows a perspective view of a second antenna duplexer according to the prior art. In the second antenna duplexer, a dielectric coaxial filter having a coaxial resonator is used as its transmitting filter 54 and a SAW filter is used as its receiving filter 55. The transmitting filter 54 and the receiving filter 55 are implemented on a circuit board 56. A matching circuit is implemented by a transmission line provided on the circuit board 56.
Because the SAW filter, which is small and light, is used as the receiving filter 55, the entire size of second antenna duplexer is small.
However, the first antenna duplexer has the separate transmitting filter 50 and receiving filter 52 provided on the circuit board 53. In addition, the dielectric coaxial filter used as the receiving filter 52 is typically large in size. The separate transmitting filter 50 and receiving filter 52 provided on the circuit board 53 and the large size of receiving filter 52 prevent the first antenna duplexer from being further reduced in size.
The second antenna duplexer separately mounts the transmitting filter 54 and the receiving filter 55 provided on the circuit board 53 and uses the dielectric coaxial filter as the transmitting filter 54. And, the dielectric coaxial filter is typically large. Like this, the second antenna duplexer is provided with such a constitution that the transmitting filter 54 and the receiving filter 55 are separately mounted on the circuit board 53, and the transmitting filter 54 is large, and furthermore a transmission line used as a matching circuit is wired on the circuit board, thereby preventing the second antenna duplexer from being further reduced in size.
The prior-art antenna duplexers have the problem that the transmitting and receiving filters separately provided on their circuit boards make it difficult to further reduce their size.
Furthermore, in the case when the dielectric coaxial filters are used the large sizes of dielectric coaxial filters used in the prior-art antenna duplexers make it more difficult to reduce the size of the duplexers.
Another problem with the prior-art antenna duplexers is that because the transmitting and receiving filters are separately provided on the circuit board, they have a large number of components and are therefore costly. Also, it is difficult to improve their reliability and stability.
In view of these problems, an object of the present invention is to provide a smaller antenna duplexer and communication apparatus that have higher antenna duplexer electric properties.
Furthermore, in view of these problems, another object of the present invention is to provide an antenna duplexer and communication apparatus that have higher antenna duplexer electric properties and improved reliability and stability.
One aspect of the present invention is an antenna duplexer comprising:
a receiving filter having a surface acoustic wave device;
a transmitting filter having a dielectric resonator; and
a matching circuit for matching said receiving filter and said transmitting filter with an antenna respectively,
wherein said transmitting filter, receiving filter, and matching circuit are integrated with each other.
Another aspect of the present invention is the antenna duplexer, wherein said matching circuit has a dielectric multilayer structure.
Still another aspect of the present invention is the antenna duplexer, wherein said transmitting filter and said matching circuit are integrated as a dielectric multilayer structure.
Yet still another aspect of the present invention is the antenna duplexer, wherein a dielectric constant of a dielectric material forming said transmitting filter is different from a dielectric constant of a dielectric material forming said matching circuit.
Still yet another aspect of the present invention is the antenna duplexer, wherein the dielectric constant of the dielectric material forming said transmitting filter is higher than the dielectric constant of the dielectric material forming said matching circuit.
A further aspect of the present invention is the antenna duplexer, wherein a relative dielectric constant of the dielectric material forming said transmitting filter is equal to or higher than 10.
A still further aspect of the present invention is the antenna duplexer, wherein the relative dielectric constant of the dielectric material forming said matching circuit is less than 10.
A yet further aspect of the present invention is the antenna duplexer, comprising a layer formed of the same material as the dielectric material forming said matching circuit,
wherein said transmitting filter is sandwiched between said matching circuit and said layer to form one integrated multilayer structure.
A still yet further aspect of the present invention is the antenna duplexer, wherein said receiving filter is formed on top of or under said matching circuit and encapsulated in a resin, and said receiving filter is electrically connected with said matching circuit.
An additional aspect of the present invention is the antenna duplexer, wherein said matching circuit is formed on top of or under said transmitting filter, and said receiving filter is electrically connected with said matching circuit.
A still additional aspect of the present invention is the antenna duplexer, wherein said matching circuit is formed on a side on which said receiving filter is formed, and said receiving filter is electrically connected with said matching circuit.
A yet additional aspect of the present invention is the antenna duplexer, wherein said receiving filter is formed adjacent to said transmitting filter in said matching circuit and encapsulated in a resin, and the receiving filter and the transmitting filter are electrically connected with the matching circuit, respectively.
A still yet additional aspect of the present invention is the antenna duplexer, wherein said receiving filter is formed in said matching circuit and encapsulated in a resin.
A supplementary aspect of te present invention is the antenna duplexer, wherein said transmitting filter and said matching circuit are connected through an edge electrode and/or a via electrode.
A still supplementary aspect of the present invention is the antenna duplexer, wherein said matching circuit has a stripline; and
said receiving filter is connected to said stripline through a via and is connected through electromagnetic coupling to a stripline leading from said antenna.
A yet supplementary aspect of the present invention is the antenna duplexer, wherein said matching circuit has a stripline; and
said transmitting filter is connected to said stripline through a via and is connected through electromagnetic coupling to said a stripline leading from said antenna.
A still yet supplementary aspect of the present invention is an antenna duplexer comprising:
a receiving filter having a composite structure of a filter having a surface acoustic wave device and a filter having a dielectric resonator;
a transmitting filter having a filter with a dielectric resonator; and
a matching circuit for matching said receiving filter and said transmitting filter with an antenna,
wherein said receiving filter, transmitting filter, and matching filter are integrated with each other.
Another aspect of the present invention is a communication apparatus comprising:
an antenna duplexer;
a transmitter circuit for outputting a transmit wave to said transmitting filter; and
a receiver circuit for inputting a receive signal provided from said receiving filter.
Still another aspect of the present invention is a communication apparatus comprising:
an antenna duplexer;
a transmitter circuit for outputting a transmit wave to said transmitting filter; and
a receiver circuit for inputting a receive signal provided from said receiving filter.